Binders are fixed on spine plates of folders and used for binding paper of which the edges are provided with holes. At present, the structure of binders used on folders is comparatively complex, and the cost of the binders used on the folders is high as well. A binder used on a folder is shown in the Chinese patent with the patent No. 99221374.6 and the patent title “Double-snap-ring File Binder”. The binder comprises a bottom plate, a left hinged plate, a right hinged plate, left rings and right rings, wherein a spring is fixed on the left hinged plate or the right hinged plate; the left hinged plate and the right hinged plate are connected with each other through a hinge; and the left rings and the right rings are fixed by the mutual fitting of clamp hooks on one sides and clamp hook grooves on the other sides and are respectively fixed on the left hinged plate and the right hinged plate. During the process of opening and closing of the binder, the left hinged plate and the right hinged plate rotate along with the left rings and the right rings respectively, and specifically, the left hinged plate and the right hinged plate rotate around articulated shafts of the left rings and the right rings respectively. As the left hinged plate and the right hinged plate of the binder are required to rotate, the binder must be provided with a base plate which is used for fixing the binder on a spine plate of the folder and also used as a mounting base plate of the left hinged plate or the right hinged plate. Therefore, the binder comprises a plurality of components, thus the cost of the binder is high.
In addition, as both the left hinged plate and the right hinged plate of the binder are movable, the opening and closing of the binder are comparatively difficult and troublesome and subjected to high resistance, thus the binder is inconvenient to use.